From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C2C9C433DB for ; Thu, 4 Feb 2021 12:04:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D422C64F4D for ; Thu, 4 Feb 2021 12:04:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235804AbhBDMEi (ORCPT ); Thu, 4 Feb 2021 07:04:38 -0500 Received: from foss.arm.com ([217.140.110.172]:57122 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235578AbhBDMEg (ORCPT ); Thu, 4 Feb 2021 07:04:36 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B6CD6D6E; Thu, 4 Feb 2021 04:03:50 -0800 (PST) Received: from [192.168.178.6] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AA3343F73B; Thu, 4 Feb 2021 04:03:48 -0800 (PST) Subject: Re: [PATCH 0/8] sched/fair: misfit task load-balance tweaks To: Valentin Schneider , Qais Yousef Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Vincent Guittot , Morten Rasmussen , Quentin Perret , Pavan Kondeti , Rik van Riel References: <20210128183141.28097-1-valentin.schneider@arm.com> <20210203151400.ommltjjyuok4yj5e@e107158-lin> From: Dietmar Eggemann Message-ID: <66efcfb1-d6ee-248a-e337-d690cda1bb5a@arm.com> Date: Thu, 4 Feb 2021 13:03:47 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/02/2021 19:43, Valentin Schneider wrote: > Hi Qais, > > On 03/02/21 15:14, Qais Yousef wrote: >> On 01/28/21 18:31, Valentin Schneider wrote: >>> Hi folks, >>> >>> Here is this year's series of misfit changes. On the menu: >>> >>> o Patch 1 is an independent active balance cleanup >>> o Patch 2 adds some more sched_asym_cpucapacity static branches >>> o Patch 3 introduces yet another margin for capacity to capacity >>> comparisons >>> o Patches 4-6 build on top of patch 3 and change capacity comparisons >>> throughout misfit load balancing >>> o Patches 7-8 fix some extra misfit issues I've been seeing on "real" >>> workloads. >>> >>> IMO the somewhat controversial bit is patch 3, because it attempts to solve >>> margin issues by... Adding another margin. This does solve issues on >>> existing platforms (e.g. Pixel4), but we'll be back to square one the day >>> some "clever" folks spin a platform with two different CPU capacities less than >>> 5% apart. >> >> One more margin is a cause of apprehension to me. But in this case I think it >> is the appropriate thing to do now. I can't think of a scenario where this >> could hurt. >> > > Thanks for having a look! > >> Thanks >> >> -- >> Qais Yousef How did you verify the benefit of these changes? It's clear that you need a platform with capacity_orig diffs <20% between CPU types (like Pixel4 - SD855 (4x261, 3x871, 1x1024) or QC's RB5 platform - SD865 (4x284, 3x871, 1*1024)) but which benchmark/testcase did you use?